This list describes how each per-cycle statistic is defined.
Per-Cycle Statistic Definitions
Cycle Number
● Units: Number
● Default axis type: Cycle Number
● Description/notes: As recorded by the tester.
Charge Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: Maximum value of time-series Charge Capacity over the cycle.
Discharge Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: Maximum value of time-series Discharge Capacity over the cycle
Minimum Test Net Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: Minimum value of time-series Test Net Capacity over the cycle.
Maximum Test Net Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: Maximum value of time-series Test Net Capacity over the cycle.
Maximum Cumulative Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: Maximum value of time-series Test Cumulative Capacity over the
cycle.
Cumulative Charge Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes:
○ Sum of all charge into the battery over the entire test.
○ Equivalent to the sum of all per-cycle Charge Capacity values, up to and
including the current cycle.
Cumulative Discharge Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes:
○ Sum of all discharge into the battery over the entire test.
○ Equivalent to the sum of all per-cycle Discharge Capacity values, up to and
including the current cycle.
Cycle Net Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: ○ Discharge Capacity - Charge Capacity for the cycle.
○ Equivalent to final value of time-series Current Cycle Net Capacity for the
cycle.
Constant Voltage Charge Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: Total amount of capacity into the battery during steps classified
as charge at constant voltage (CV) during the cycle.
Other Charge Capacity
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: Total amount of capacity into the battery during steps classified
as charge, but NOT classified as constant voltage (CV) during the cycle.
Charge Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes: Maximum value of time-series Charge Energy over the cycle.
Discharge Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes: Maximum value of time-series Discharge Energy over the cycle.
Minimum Test Net Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes: Minimum value of time-series Test Net Energy over the cycle.
Maximum Test Net Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes: Maximum value of time-series Test Net Energy over the cycle.
Maximum Cumulative Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes: Maximum value of time-series Test Cumulative Energy over the
cycle.
Cumulative Charge Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes:
○ Sum of all energy into the battery over the entire test.
○ Equivalent to the sum of all per-cycle Charge Energy values, up to and
including the current cycle.
Cumulative Discharge Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes:
○ Sum of all energy out of the battery over the entire test.
○ Equivalent to the sum of all per-cycle Discharge Energy values, up to and
including the current cycle.
Cycle Net Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes:
○ Discharge Energy - Charge Energy for the cycle.
○ Equivalent to final value of time-series Current Cycle Net Energy for the cycle.
Constant Voltage Charge Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes: Total amount of energy into the battery during steps classified as
charge at constant voltage (CV) during the cycle.
Other Charge Energy
● Units: Watt-hours (Wh)
● Default axis type: Energy
● Description/notes: Total amount of energy into the battery during steps classified as
charge, but NOT classified as constant voltage (CV) during the cycle.
Coulombic Efficiency
● Units: Percent (%)
● Default axis type: Efficiency
● Description/notes: Computed as per-cycle Discharge Capacity / Charge Capacity for
the current cycle.
Energy Efficiency
● Units: Percent (%)
● Default axis type: Efficiency
● Description/notes: Computed as per-cycle Discharge Energy / Charge Energy for the
current cycle.
Voltage Efficiency
● Units: Percent (%)
● Default axis type: Efficiency
● Description/notes:
○ Computed as per-cycle Energy Efficiency / Coulombic Efficiency for the
current cycle.
○ Equal to Mean Discharge Potential (capacity-weighted) / Mean Charge
Potential (capacity-weighted).
Minimum Potential
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Minimum value of time-series Potential over the cycle.
Maximum Potential
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Maximum value of time-series Potential over the cycle.
Initial Charge Potential
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Value of time-series Potential at the beginning of the first step
classified as charge (Current > 0) in a cycle
Final Charge Potential
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Value of time-series Potential at the end of the last step classified
as charge (Current > 0) in a cycle
Initial Discharge Potential
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Value of time-series Potential at the beginning of the first step
classified as discharge (Current < 0) in a cycle
Final Discharge Potential
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Value of time-series Potential at the end of the last step classified
as discharge (Current < 0) in a cycle
Open Circuit Potential - Charge
● Units: Volts (V)
● Default axis type: Potential
● Description/notes:
○ Value of time-series Potential at the end of a rest step (Current = 0) that
follows charge.
○ If multiple charge-rest transitions occur during the cycle, this value is
calculated during the rest step of the last such transition.
Open Circuit Potential - Discharge
● Units: Volts (V)
● Default axis type: Potential
● Description/notes:
○ Value of time-series Potential at the end of a rest step (Current = 0) that
follows discharge.
○ If multiple discharge-rest transitions occur during the cycle, this value is
calculated during the rest step of the last such transition.
Relaxation Potential - Charge
● Units: Volts (V)
● Default axis type: Potential
● Description/notes:
○ Time-series Potential value from the first datapoint at the beginning of a rest
step (Current = 0) following charge.
○ If multiple charge-rest transitions occur during the cycle, this value is
calculated during the rest step of the last such transition.
Relaxation Potential - Discharge
● Units: Volts (V)
● Default axis type: Potential
● Description/notes:
○ Time-series Potential value from the first datapoint at the beginning of a rest
step (Current = 0) following discharge.
○ If multiple discharge-rest transitions occur during the cycle, this value is
calculated during the rest step of the last such transition.
Mean Charge Potential (time-weighted)
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Time-weighted average of Potential during charge steps (Current
> 0) over the cycle.
Mean Discharge Potential (time-weighted)
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Time-weighted average of Potential during discharge steps
(Current < 0) over the cycle.
Mean Charge Potential (capacity-weighted)
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Capacity-weighted average of Potential during charge steps
(Current > 0) over the cycle.
Mean Discharge Potential (capacity-weighted)
● Units: Volts (V)
● Default axis type: Potential
● Description/notes: Capacity-weighted average of Potential during discharge steps
(Current < 0) over the cycle.
Minimum Charge Current
● Units: Amperes (A)
● Default axis type: Current
● Description/notes: Least positive value of Current over all steps classified as charge
(Current > 0) in a cycle.
Maximum Charge Current
● Units: Amperes (A)
● Default axis type: Current
● Description/notes: Most positive value of Current over all steps classified as charge
(Current > 0) in a cycle.
Mean Charge Current (time-weighted)
● Units: Amperes (A)
● Default axis type: Current
● Description/notes: Time-weighted average of Current over all steps classified as
charge (Current > 0) in a cycle.
Minimum Discharge Current
● Units: Amperes (A)
● Default axis type: Current
● Description/notes: Least negative value of Current over all steps classified as
discharge (Current < 0) in a cycle.
Maximum Discharge Current
● Units: Amperes (A)
● Default axis type: Current
● Description/notes: Most negative value of Current over all steps classified as discharge
(where Current < 0) in a cycle.
Mean Discharge Current (time-weighted)
● Units: Amperes (A)
● Default axis type: Current
● Description/notes: Time-weighted average of Current over all steps classified as
discharge (Current < 0) in a cycle.
Cycle Start Time
● Units: Time (h)
● Default axis type: Time
● Description/notes: Test Time of the first datapoint in a cycle.
Cycle End Time
● Units: Time (h)
● Default axis type: Time
● Description/notes: Test Time of the last datapoint in a cycle.
Cycle Start Timestamp
● Units: Datetime (mm/dd/yy hh:mm:ss)
● Default axis type: Timestamp
● Description/notes: Timestamp of the first datapoint in a cycle.
Cycle End Timestamp
● Units: Datetime (mm/dd/yy hh:mm:ss)
● Default axis type: Timestamp
● Description/notes: Timestamp of the last datapoint in a cycle.
Constant Voltage Charge Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total time of all test program steps where Current > 0 and
potential is constant (defined as stdev(V) / mean(V) < 0.001 for each step) over the
cycle.
Other Charge Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total time of all test program steps where Current > 0 and
potential is not constant over the cycle.
Total Charge Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total time of all test program steps where Current > 0 over the
cycle.
Constant Voltage Discharge Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total time of all test program steps where Current < 0 and
potential is constant (defined as stddev(V) / mean(V) < 0.001 for each step) over the
cycle.
Other Discharge Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total time of all test program steps where Current < 0 and
potential is not constant over the cycle.
Total Discharge Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total time of all test program steps where Current < 0 over the
cycle.
Rest Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total time of all test program steps where Current = 0 over the
cycle.
Other Cycle Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total time of all test program steps which are not classifiable as
solely charge (Current > 0), discharge (Current < 0), or rest (Current = 0).
Total Cycle Time
● Units: Hours (h)
● Default axis type: Time
● Description/notes: Total elapsed time over the cycle.
Maximum Charge Power
● Units: Watts (W)
● Default axis type: Power
● Description/notes: Most positive value of Power over all steps classified as charge
(where Current > 0) in a cycle.
Minimum Charge Power
● Units: Watts (W)
● Default axis type: Power
● Description/notes: Least positive value of Power over all steps classified as charge
(where Current > 0) in a cycle.
Maximum Discharge Power
● Units: Watts (W)
● Default axis type: Power
● Description/notes: Most negative value of time-series Power over all steps classified
as discharge (where Current < 0) in a cycle.
Minimum Discharge Power
● Units: Watts (W)
● Default axis type: Power
● Description/notes: Least negative value of Power over all steps classified as discharge
(where Current < 0) in a cycle.
Mean Charge Power (time-weighted)
● Units: Watts (W)
● Default axis type: Power
● Description/notes: Mean value of Power over all steps classified as charge (Current >
0) in a cycle.
Mean Discharge Power (time-weighted)
● Units: Watts (W)
● Default axis type: Power
● Description/notes: Mean value of Power over all steps classified as discharge (Current
< 0) in a cycle.
Internal Resistance Start of Charge
● Units: Ohms (Ω)
● Default axis type: Resistance
● Description/notes:
○ Pseudo-internal resistance measurement at start of first charge step in a
cycle.
○ Computed using Ohm’s law, such that R = ∆V / ∆I, where ∆V is the potential
difference between the start of charge and the last datapoint of the step
prior to charge, and ∆I is the difference in current between the last datapoint
before the start of the charge step and the first datapoint of the charge step.
Internal Resistance End of Charge
● Units: Ohms (Ω)
● Default axis type: Resistance
● Description/notes:
○ Pseudo-internal resistance measurement at end of last charge step in a cycle.
○ Computed using Ohm’s law, such that R = ∆V / ∆I, where ∆V is the potential
difference between the end of charge and the first datapoint of the step
following charge, and ∆I is the difference in current between the last
datapoint during the charge step and the first datapoint following the charge
step.
Internal Resistance Start of Discharge
● Units: Ohms (Ω)
● Default axis type: Resistance
● Description/notes:
○ Pseudo-internal resistance measurement at start of first discharge step in a
cycle.
○ Computed using Ohm’s law, such that R = ∆V / ∆I, where ∆V is the potential
difference between the start of discharge and the last datapoint of the step
prior to discharge, and ∆I is the difference in current between the last
datapoint before the start of the discharge step and the first datapoint of the
discharge step.
Internal Resistance End of Discharge
● Units: Ohms (Ω)
● Default axis type: Resistance
● Description/notes:
○ Pseudo-internal resistance measurement at end of last discharge step in a
cycle.
○ Computed using Ohm’s law, such that R = ∆V / ∆I, where ∆V is the potential
difference between the end of discharge and the first datapoint of the step
following discharge, and ∆I is the difference in current between the last
datapoint during the discharge step and the first datapoint following the
discharge step.
Discharge Capacity (temperature-compensated)
● Units: Amp-hours (Ah)
● Default axis type: Capacity
● Description/notes: BCI-06 formula for temperature compensation, with 27 °C
as the reference temperature:
Qc= Qr [1 - (0.009 (Tf - 27))]
Where
Qc= Discharge Capacity (temperature-compensated), in Ah
Qr= Discharge Capacity, in Ah
Tf = Temperature at last discharge point in cycle, in °C
Total Discharge Time (temperature-compensated)
● Units: Hours (h)
● Default axis type: Time
● Description/notes: BCI-06 formula for temperature compensation, with 27 °C
as the reference temperature:
Mc= Mr [1 - (0.009 (Tf - 27))]
Where
Mc= Total Discharge Time (temperature-compensated), in h
Mr= Total Discharge Time, in h
Tf = Temperature at last discharge point in cycle, in °C
Important Note on Cycle Aggregations
In analyzing time-series data to produce per-cycle statistics, Voltaiq makes certain
assumptions about the cycling test program. For some cycling tests these assumptions will be incorrect, and thus meaningful values cannot be computed for certain per-cycle
statistics.
If the Voltaiq cycle analytics cannot compute a meaningful value for a certain per-cycle
statistic, a null value is recorded in Voltaiq for that particular data field and cycle record.
When plotted in Voltaiq, any null value will not appear in the plot.
The following are examples of assumptions built into the Voltaiq cycle analytics algorithms:
These statistics require a rest step immediately following charge
● Open Circuit Potential - Charge
● Relaxation Potential - Charge
These statistics require a rest step immediately following discharge
● Open Circuit Potential - Discharge
● Relaxation Potential - Discharge